Getting back on topic, I have to say I don't understand Soulsborne fans who insist that there is something about these games that is uniquely groundbreaking or paradigm changing. I mean, I love these series, mind you, but at best they can be described as eclectic rather than innovative. Fundamentally, the Dark Souls series is an eccentric combination of a heavily slowed-down and more methodical version of Japanese hack-and-slash combat conventions, exploration structured in the Metroidvania style, some classical dungeon crawling RPG tropes thrown in for good measure (the legacy of the King's Field series) and some RPG elements in the form of a simple but intuitive character system that offers a surprising amount of variety in playstyles, even compared to Action RPGs. I have always found it odd that people consider it a combat-centric game, let alone "the hard game". It is not a particularly hard game for anyone with gaming experience, even if it does comfortably dodge the charge of being easy, and the combat itself is by no means among the best: hack-and-slashes, fighting games, shmups, and many other genres beat it easily in terms of the mechanical depth of combat. To me what sets these games apart and makes them so good is how the weave together all of these elements into a consistent experience that is all around very solid and with very few weak links, and especially the way it links together its slow, methodical combat with exploration: what makes the game most challenging and mechanically interesting is not individual fights themselves, but the tightly designed encounters which simultaneously integrate many factors such as the environment, positioning, traps, etc. into puzzles in real time. As I put it in another thread:
That said DD could also learn a bit from Dark Souls, one thing that Dark Souls does very well - apart from the depth of the combat mechanics - that I rarely see in DD is designing tactical encounters. Like, for example, in Dark Souls areas are designed with the explicit intent to screw you: you have enemies in plain sight that act as bait, guys hiding in ambush waiting to skewer you, campy fucks shooting and throwing crap at you, sometimes environmental hazards and traps, cramped environments and limited field of view, and all of those factors and more engineered to operate in unison according to the Dungeon Master's sadistic plan to bar you from getting through with your estus filled, if at all. Though to be fair, this works for Dark Souls due to the nature of its exploration as a dungeon crawler.
There ain't no such thing as a fair fight in Souls. It is not a duelist's game. I would also add that it is not only the emphasis on dungeon exploration that permits such tactical encounters, but also the slow, ponderous, and high-lethality nature of the combat which makes it more deliberate that most action games. In fact, Dark Souls is probably the closest a real time game has come to providing 'encounter design' in the sense we use the term for tactical RPGs. Choices regarding the order in which enemies are engaged, whether to press onward or secure the flanks, scout the area ahead, etc tend to be more rewarding in Dark Souls than in the combat genres mentioned above which rather emphasize pitched battles and quick reflexes. There is definitely an element of that in Souls, but through the encounter design it is elegantly enmeshed into the dungeon exploration itself. Like in old-school crawlers, the dungeon is the enemy, but the interesting spin on the formula comes in the way that enemies themselves are the dungeon.
The dungeons themselves are nowhere nearly as complex as they are in, say, old-school blobbers, but as I mentioned, the way that the dungeon exploration itself is structured is more like that of a Metroidvania than Wiz-like crawlers in that there are puzzles within puzzles within puzzles that offer layered complexity rather than the discrete instances of expansive complexity found in the Wizardry formula. What I mean by this is that in Metroidvanias you have individual maze-like areas that are puzzles in their own right, but those areas themselves in turn are part of a broader puzzle that is the interconnected world. But that is not all, apart from those two layers of puzzles there is yet another, which is the combination, within individual areas, of platforming, combat, and physical puzzles that are solved through interactive systems(like the Grapple beam, Morph Ball, etc, in Metroid). Dark Souls lacks the platforming and physical puzzle element but compensates for it through the tactical puzzles that I mentioned above and that work through the combination of enemy placement, traps, and disorientation. Also, like Metroidvanias, DS emphasizes freeform gameplay which means that sequence breaks, branching exploration, and different possible solutions to situations are ubiquitous. Therefore, while the net complexity in level design does not ultimately match Wizardry-likes or fully-fledged Metroidvanias like the Metroid series, it is still an impressive achievement when one considers that this design also incorporates very solid combat, a serviceable character system and resource management.
Oh, I haven't discussed that last aspect, which I also think is executed in an impressive way. I think the combination of Estus management and bonfire checkpoints is a clever approach(and FWIW, surprisingly not unimmersive) for dealing with the issue of resource managament that sometimes plagues both RPGs and Metroidvanias. The checkpoints themselves are a riff on the old save stations and not very innovative, and while the idea of automatically replenishable consumables seems novel, it actually isn't that different from spells that are recharged on rest. But due to the way this system is impemented(nigh impossibility of obtaining healing from downed enemies), the result is a well-balanced resource management component that enhances dungeon strategy further, not to mention that it is one of those rare cases in which consumables are implemented as an essential part of the game's design rather than a crutch uncomfortably tacked in. To be fair though, this point largely applies to the Dark Souls series itself, as Bloodborne and DeS use a more generic - and IMO degenerate - system of consumables.
Ultimately if someone said that Dark Souls is not excellent at any particular aspect of gameplay, but merely good at many things, I would say fair enough, though I would point out that a game that does so many things well like DS does is extremely rare, and not only in our days. Abominations of bloated design are almost always the result of such ambitious projects, rather than something as well-rounded as Dark Souls. Beyond that, I would also point out that what makes the series special is the sum of the - already good - parts or how it brings them all together in such a seamless and consistent way. And it is not only the synergies between the dungeon design, the tactics, the combat, the character building, and resource management, but heck, even the lore, story and world building pile in and fuse themselves into the mechanics in an impressively interactive way. An example, the way the game, like PS:T, acknowledges that your character dies and keeps coming back which indicates the unison of the narrative with the "ironman" mechanic, or the way that hollows are implied to have been guys exactly like you, but who gave up and went mad, acknowledging the hostile nature of the world's design, of which they themselves are a part. All of this without getting into the NPC questlines.
The cohesive nature of the game's overarching design along with the quality of every individual aspect of it are what I have always found to be the most impressive things about this series, much more than the combat or the much vaunted difficulty (greatly exaggerated in any case). If anything the games I find most comparable to the Souls series are not hack-and-slashes like Ninja Gaiden, but rather 3D Metroidvanias like the Metroid Prime series (a tiny niche within a niche in and of itself), and even then the differences are substantial. These games are not particularly hard, or particularly innovative, and they might well not be RPGs, what they definitely are, however, is very well designed games.